1. Field of the Invention
This invention relates to apparatus for exchanging a billet-guiding roller for another in a plant for continuous casting. Said apparatus comprises a handling head, which is adapted to be coupled to a dummy bar and movable with the dummy bar through an array of guide rollers, and which carries two arms, each of which is pivoted on an axis which is parallel to the billet-guiding rollers and is provided with a holder for holding a billet-guiding roller. Said handling head also carries arm-driving means for imparting a pivotal movement to said arms.
2. Description of the Prior Art
In a continuous casting plant it is difficult to remove and install a single billet-guiding roller or guide roller, particularly at the curved portion of the path along which the billet is guided. This difficulty is due to the fact that the guide rollers are relatively closely spaced apart and the arrangement is such that they can be moved to and from their installed position only between the outer and inner curved series of such rollers rather than on the outside of the array formed by said rollers. The exchange of a guide roller is usually effected by means of a handling head, which is provided with a holder for holding a guide roller and which is coupled to the dummy bar, which is otherwise employed to initiate the casting operation. The handling head can then be pulled together with the dummy bar through the array of guide rollers. To permit a removal of a guide roller and a movement of a new guide roller to the position previously occupied by the guide roller which has been removed in such a manner that the handling head is not actuated to remove the old roller from the array of guide rollers until the new roller has been installed in said array, it has been proposed to use an exchanging apparatus (Austrian patent specification No. 362,541) which comprises a handling head, which carries two arms, which are arranged on behind the other and are pivoted on parallel axes and provided with respective holders for holding respective guide rollers, and which also carries arm-driving means for imparting a pivotal movement to said arms. By means of such a handling head the new guide roller can be moved to the desired location and can be exchanged with the old guide roller in a single operation. But as one of the two pivoted arms is pivoted to the end of the handling head and protrudes from the handling head in the longitudinal direction of the array of guide rollers, the exchanging apparatus has a considerable overall length, particularly because additional space is required for the arm-driving means, which consist of actuating cylinders, which are pivoted at one end to the handling head and at the other end to the pivoted arm. Besides, the guide roller holders provided on the pivoted arms must embrace the guide rollers around more than 180.degree. so that the overall height of the handling head cannot be reduced below a certain minimum. For these reasons the known exchanging apparatus has only a restricted field of application and which are closely spaced along along a curved section of the path for the billet because in that region the permissible overall height and overall length of the handling head will be restricted by the spacing of the outer and inner curved series of guide rollers.